Registration Dossier
Registration Dossier
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EC number: 203-497-4 | CAS number: 107-51-7
Endpoint summary
Administrative data
Key value for chemical safety assessment
Genetic toxicity in vitro
Description of key information
Data are available for octamethyltrisiloxane from reliable in vitro
studies for mutagenicity to bacteria and cytogenicity in mammalian
cells. No further information is available for the registered substance;
however, reliable data are available for the closely related substances
hexamethyldisiloxane (CAS 107-46-0) and decamethyltetrasiloxane (CAS
141-62-8).
Gene mutation (Bacterial reverse mutation assay / Ames test): negative
with and without activation in Salmonella typhimurium strains TA 98,
100, 1535, 1537 and E.coli WP2 uvrA (OECD TG 471) (Wagner (2008)).
Cytogenicity in mammalian cells: negative with and without metabolic
activation in CHO cells (OECD TG 473) (Madraymootoo and Rao (2008)).
Mutagenicity in mammalian cells: read-across from structural analogue
hexamethyldisiloxane: negative in L5178Y mouse lymphoma cells (similar
to OECD TG 476) (Litton Bionetics (1978)).
Mutagenicity in mammalian cells: read-across from structural analogue
decamethyltetrasiloxane: negative in L5178Y mouse lymphoma cells (OECD
TG 476) (Flanders, L. (2010)).
Link to relevant study records
- Endpoint:
- in vitro gene mutation study in bacteria
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- 2007-12-28 - 2008-01-23
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- guideline study
- Qualifier:
- according to guideline
- Guideline:
- OECD Guideline 471 (Bacterial Reverse Mutation Assay)
- GLP compliance:
- yes (incl. QA statement)
- Type of assay:
- bacterial reverse mutation assay
- Species / strain / cell type:
- S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
- Species / strain / cell type:
- E. coli WP2 uvr A
- Metabolic activation:
- with and without
- Metabolic activation system:
- Aroclor 1254 induced rat liver S9
- Test concentrations with justification for top dose:
- 50, 150, 500, 1500 and 5000 µg/plate
- Vehicle / solvent:
- - Vehicle(s)/solvent(s) used: Acetone
- Justification for choice of solvent/vehicle: none given - Untreated negative controls:
- no
- Negative solvent / vehicle controls:
- yes
- True negative controls:
- no
- Positive controls:
- yes
- Positive control substance:
- other: 2-aminoanthracene 1 µg/plate
- Remarks:
- TA98, TA100, TA1535 and TA1537 with metabolic activation
- Untreated negative controls:
- no
- Negative solvent / vehicle controls:
- yes
- True negative controls:
- no
- Positive controls:
- yes
- Positive control substance:
- other: 2-aminoanthracene 10 µg/plate
- Remarks:
- WP2 uvrA with metabolic activation
- Untreated negative controls:
- no
- Negative solvent / vehicle controls:
- yes
- True negative controls:
- no
- Positive controls:
- yes
- Positive control substance:
- 2-nitrofluorene
- Remarks:
- TA98 without metabolic activation: 1 µg/plate
- Untreated negative controls:
- no
- Negative solvent / vehicle controls:
- yes
- True negative controls:
- no
- Positive controls:
- yes
- Positive control substance:
- sodium azide
- Remarks:
- TA100 and TA1535 without metabolic activation: 1 µg/plate
- Untreated negative controls:
- no
- Negative solvent / vehicle controls:
- yes
- True negative controls:
- no
- Positive controls:
- yes
- Positive control substance:
- 9-aminoacridine
- Remarks:
- TA1537 without metabolic activation: 75 µg/plate
- Untreated negative controls:
- no
- Negative solvent / vehicle controls:
- yes
- True negative controls:
- no
- Positive controls:
- yes
- Positive control substance:
- methylmethanesulfonate
- Remarks:
- WP2 uvrA without metabolic activation: 1000 µg/plate
- Details on test system and experimental conditions:
- METHOD OF APPLICATION: in agar (plate incorporation)
ACTIVATION: S9 mix contained 10% S9, and glucose-6-phosphate and NADP as co-factors. 0.5 ml S9 mix was added to 2.0 ml top agar giving a final concentration of approximately 2% S9.
DURATION
- Exposure duration: 48 - 72 hours
NUMBER OF REPLICATIONS: experiment 1 - duplicate plates, experiment 2 - triplicate plates
DETERMINATION OF CYTOTOXICITY
- Method: other: condition of background lawn - Evaluation criteria:
- A result is positive if the mean of each positive control exhibits at least a 3-fold increase in the number of revertants over the mean value of the respective vehicle control. A minimum of three non-toxic dose levels were required to evaluate assay data. Strains TA1535 and TA1537 were judged positive if there was a 3-fold increase in the number of revertants compared with the mean vehicle control value and a 2-fold increase for Salmonella typhimurium strains TA98, TA100 and E. coli WP2 uvrA.
- Statistics:
- None stated in report
- Key result
- Species / strain:
- S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
- Metabolic activation:
- with and without
- Genotoxicity:
- negative
- Cytotoxicity / choice of top concentrations:
- no cytotoxicity nor precipitates, but tested up to recommended limit concentrations
- Vehicle controls validity:
- valid
- Untreated negative controls validity:
- not applicable
- Positive controls validity:
- valid
- Key result
- Species / strain:
- E. coli WP2 uvr A
- Metabolic activation:
- with and without
- Genotoxicity:
- negative
- Cytotoxicity / choice of top concentrations:
- no cytotoxicity nor precipitates, but tested up to recommended limit concentrations
- Vehicle controls validity:
- valid
- Untreated negative controls validity:
- not applicable
- Positive controls validity:
- valid
- Additional information on results:
- TEST-SPECIFIC CONFOUNDING FACTORS
COMPARISON WITH HISTORICAL CONTROL DATA: Historical negative and positive control values included in report
ADDITIONAL INFORMATION ON CYTOTOXICITY: Cytotoxicity was not evident at any concentration - Conclusions:
- Octamethyltrisiloxane has been tested for mutagenicity to bacteria in a study which was conducted according to OECD 471, and in compliance with GLP. No evidence of a test substance related increase in the number of revertants was observed with or without activation in the initial or the repeat experiments with Salmonella typhimurium strains TA 98, 100, 1535, 1537 and E.coli WP2 uvrA. Appropriate positive and solvent controls were tested and gave expected results. It is concluded that the test substance is negative for mutagenicity to bacteria under the conditions of the test.
- Endpoint:
- in vitro cytogenicity / chromosome aberration study in mammalian cells
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- 2008-10-07 - 2008-10-26
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- guideline study
- Qualifier:
- according to guideline
- Guideline:
- OECD Guideline 473 (In Vitro Mammalian Chromosome Aberration Test)
- Qualifier:
- according to guideline
- Guideline:
- other: EPA (TSCA) GLP 40 CFR Part 792
- GLP compliance:
- yes (incl. QA statement)
- Type of assay:
- in vitro mammalian chromosome aberration test
- Species / strain / cell type:
- Chinese hamster Ovary (CHO)
- Details on mammalian cell type (if applicable):
- - Type and identity of media: McCoy's 5A medium inc 10% FBS, 100 units penicillin/ml, 100 µg streptomycin/ml, 2mM L-glutamine
- Properly maintained: yes
- Periodically checked for Mycoplasma contamination: yes
- Periodically checked for karyotype stability: yes, cell stocks not used beyond passage 20 to ensure karyotype stability
- Periodically "cleansed" against high spontaneous background: no information - Metabolic activation:
- with and without
- Metabolic activation system:
- Aroclor 1254 induced rat liver S9
- Test concentrations with justification for top dose:
- 4 hours (-MA): 2.5, 5, 12.5 µg/ml; 20 hours (-MA): 5, 10, 15 µg/ml; 4 hours (+MA): 10, 25 and 75 µg/ml.
- Vehicle / solvent:
- - Vehicle(s)/solvent(s) used: Acetone
- Justification for choice of solvent/vehicle: none given in report - Untreated negative controls:
- no
- Negative solvent / vehicle controls:
- yes
- True negative controls:
- no
- Positive controls:
- yes
- Positive control substance:
- mitomycin C
- Remarks:
- 4 hours without metabolic activation: 0.2 µg/ml
- Untreated negative controls:
- no
- Negative solvent / vehicle controls:
- yes
- True negative controls:
- no
- Positive controls:
- yes
- Positive control substance:
- cyclophosphamide
- Remarks:
- 4 hours with metabolic activation: 10 µg/ml
- Untreated negative controls:
- no
- Negative solvent / vehicle controls:
- yes
- True negative controls:
- no
- Positive controls:
- yes
- Positive control substance:
- mitomycin C
- Remarks:
- 20 hours without metabolic activation: 0.1 µg/ml
- Details on test system and experimental conditions:
- METHOD OF APPLICATION: in medium
DURATION
- Expression time (cells in growth medium): 48 hours
- Selection time (if incubation with a selection agent):
- Fixation time (start of exposure up to fixation or harvest of cells): 24 hours
SPINDLE INHIBITOR (cytogenetic assays): Colcemid
STAIN (for cytogenetic assays): 5% Giemsa
NUMBER OF REPLICATIONS: duplicate cultures
NUMBER OF CELLS EVALUATED: 200 per dose level
DETERMINATION OF CYTOTOXICITY
- Method: cell growth inhibition
ACTIVATION:
Aroclor 1254-induced rat liver S9: S9 mix included glucose-6-phosphate and NADP as co-factors. - Evaluation criteria:
- The test article was considered to induce a positive response when the percentage of cells with aberrations was increased in a dose responsive manner with one or more concentrations being statistically significant (p<0.05). Values that are statistically significant but do not exceed the range of historical solvent controls may be judged as not biologically significant.
- Statistics:
- Fisher's Exact test and the Cochran-Armitage test to measure dose responsiveness.
- Key result
- Species / strain:
- Chinese hamster Ovary (CHO)
- Metabolic activation:
- with and without
- Genotoxicity:
- negative
- Cytotoxicity / choice of top concentrations:
- cytotoxicity
- Remarks:
- Substantial cytotoxicity observed at dose levels > 23.4 µg/ml in all three treatment groups
- Vehicle controls validity:
- valid
- Untreated negative controls validity:
- not applicable
- Positive controls validity:
- valid
- Additional information on results:
- TEST-SPECIFIC CONFOUNDING FACTORS
- Effects of pH: pH of highest concentration approximately 7.5
- Effects of osmolality: considered acceptable, 2340 µg/ml was 281 mmol/kg, and did not exceed the osmolality of the solvent by more than 20%
- Precipitation: Visible precipitate in the form of oily droplets observed in treatment medium at 2340 µg/ml, dose levels < 702 µg/ml were soluble in treatment medium.
- Other confounding effects: none
RANGE-FINDING/SCREENING STUDIES:
COMPARISON WITH HISTORICAL CONTROL DATA: included in report
ADDITIONAL INFORMATION ON CYTOTOXICITY: - Conclusions:
- Octamethyltrisiloxane has been tested in a reliable in vitro cytogenetic assay according to OECD TG 473 and under GLP. The test substance did not induce statistically and biologically significant increases in the chromosomal aberration frequency in CHO cells. Appropriate solvent and positive controls were included and gave expected results. It is concluded that the test substance is negative for the induction of chromosome aberrations (is not clastogenic) in vitro under the conditions of the test.
- Endpoint:
- in vitro gene mutation study in mammalian cells
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- comparable to guideline study with acceptable restrictions
- Remarks:
- The restrictions were that the test concentrations were not duplicated.
- Qualifier:
- equivalent or similar to guideline
- Guideline:
- OECD Guideline 476 (In Vitro Mammalian Cell Gene Mutation Test)
- Deviations:
- yes
- Remarks:
- no duplicates
- GLP compliance:
- no
- Type of assay:
- mammalian cell gene mutation assay
- Species / strain / cell type:
- mouse lymphoma L5178Y cells
- Metabolic activation:
- with and without
- Metabolic activation system:
- mouse liver S9
- Test concentrations with justification for top dose:
- 0.0125, 0.025, 0.05, 0,1, 0.2 µl/ml
- Vehicle / solvent:
- - Vehicle(s)/solvent(s) used: ethanol
- Untreated negative controls:
- yes
- Negative solvent / vehicle controls:
- yes
- True negative controls:
- no
- Positive controls:
- yes
- Positive control substance:
- ethylmethanesulphonate
- Remarks:
- without activation
- Untreated negative controls:
- yes
- Negative solvent / vehicle controls:
- yes
- True negative controls:
- no
- Positive controls:
- yes
- Positive control substance:
- N-dimethylnitrosamine
- Remarks:
- with activation
- Details on test system and experimental conditions:
- METHOD OF APPLICATION: in medium
DURATION
- Exposure duration: 4 hours
- Expression time (cells in growth medium): 3 days
- Selection time (if incubation with a selection agent): 10 days
SELECTION AGENT (mutation assays): BUdR
NUMBER OF REPLICATIONS: no replicates
DETERMINATION OF CYTOTOXICITY
- Method: other: loss of growth potential - Evaluation criteria:
- A substance is considered mutagenic if there is a dose response relationship over 3 dose levels; minimum increase at high level of dose response is at least 2.5 times greater than the solvent control value; solvent control data are within normal range of spontaneous background mutation rates.
- Statistics:
- No statistical analysis was carried out.
- Key result
- Species / strain:
- mouse lymphoma L5178Y cells
- Metabolic activation:
- with and without
- Genotoxicity:
- negative
- Cytotoxicity / choice of top concentrations:
- cytotoxicity
- Remarks:
- at 0.2 µl/ml, equiv to approx 200 µg/ml
- Vehicle controls validity:
- valid
- Untreated negative controls validity:
- valid
- Positive controls validity:
- valid
- Additional information on results:
- Preliminary cytotoxicity testing indicated toxicity at > 0.2 µl/ml
Several scattered increases were thought by the authors to be the result of spurious fluctuations and cytotoxicity. - Conclusions:
- Hexamethyldisiloxane has been tested for mutagenicity in L5178Y cells in a valid and reliable study according to a protocol that is similar to OECD TG 476. The test substance did not cause a biologically significant increase in the mutation frequency; solvent and positive controls gave expected results. It is concluded that the test substance is not mutagenic under the conditions of the test.
- Endpoint:
- in vitro gene mutation study in mammalian cells
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- 11 August 2009 to 14 September 2009
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- guideline study
- Qualifier:
- according to guideline
- Guideline:
- OECD Guideline 476 (In Vitro Mammalian Cell Gene Mutation Test)
- Deviations:
- no
- GLP compliance:
- yes (incl. QA statement)
- Type of assay:
- mammalian cell gene mutation assay
- Species / strain / cell type:
- mouse lymphoma L5178Y cells
- Metabolic activation:
- with and without
- Metabolic activation system:
- phenobarbital and beta-naphthoflavone-induced rat liver S9
- Test concentrations with justification for top dose:
- 12.5-200 µg/ml (4h) and 1.56-50 µg/ml (24h)
- Vehicle / solvent:
- - Vehicle(s)/solvent(s) used: ethanol;
- Justification for choice of solvent/vehicle: none given in study report - Untreated negative controls:
- no
- Negative solvent / vehicle controls:
- yes
- True negative controls:
- no
- Positive controls:
- yes
- Positive control substance:
- ethylmethanesulphonate
- Remarks:
- without metabolic activation 400 µg/ml (4 h exposure), 150 µg/ml (24 h exposure)
- Untreated negative controls:
- no
- Negative solvent / vehicle controls:
- yes
- True negative controls:
- no
- Positive controls:
- yes
- Positive control substance:
- cyclophosphamide
- Remarks:
- with metabolic activation 2 µg/ml
- Details on test system and experimental conditions:
- METHOD OF APPLICATION: in medium
DURATION
- Exposure duration: 4 h (with and without metabolic activation); 24 h (without metabolic activation)
- Expression time (cells in growth medium): 2 days
- Selection time (if incubation with a selection agent): 10-14 days:
SELECTION AGENT (mutation assays): 5-trifluorothymidine
NUMBER OF REPLICATIONS: duplicate cultures
DETERMINATION OF CYTOTOXICITY
- Method: relative total growth; other: % viability
OTHER EXAMINATIONS:
- Other: number of small and large colonies
OTHER: a preliminary toxicity assay was conducted up to a concentration of 3107 µg/ml (10 mM) - Evaluation criteria:
- For a test material to demonstrate a mutagenic response it must produce a reproducible and dose-dependent statistically significant increase in the induced mutant frequency (IMF) over the concurrent vehicle mutant frequency value, exceeding the Global Evaluation Factor (GEF) value of 126 E10-06.
- Statistics:
- UKEMS statistical package used.
- Species / strain:
- mouse lymphoma L5178Y cells
- Metabolic activation:
- with and without
- Genotoxicity:
- negative
- Cytotoxicity / choice of top concentrations:
- cytotoxicity
- Remarks:
- 12 - 24 µg/ml (24h)
- Vehicle controls validity:
- valid
- Untreated negative controls validity:
- not applicable
- Positive controls validity:
- valid
- Additional information on results:
- TEST-SPECIFIC CONFOUNDING FACTORS
- Effects of pH: no marked change in pH was observed
- Effects of osmolality: did not increase by more than 50 mOsm
- Precipitation: a non-interfering precipitate of the test material observed at and above 100 μg/ml in the absence of metabolic activation, and at and above 150 μg/ml in the presence of metabolic activation.
- Other confounding effects: none
RANGE-FINDING/SCREENING STUDIES: No dose-related toxicity was observed following 4 h exposure; marked toxicity was observed in the 24 h exposure group.
COMPARISON WITH HISTORICAL CONTROL DATA: Control results were within the range of historical controls - Remarks on result:
- other: all strains/cell types tested
- Conclusions:
- Interpretation of results:
negative with and without metabolic activation
Decamethyltetrasiloxane has been tested according to OECD TG 476 and under GLP conditions for mutagenicity to mouse lymphoma L5178Y cells up to cytotoxic concentrations. No increase in mutant frequency was detected at any concentration after 4h exposure with and without metabolic activation and 24 h exposure without metabolic activation. Appropriate solvent and positive controls were included and gave expected results. It is concluded that the test substance is negative for the induction of mutations in L5178Y cells under the conditions of the test.
Referenceopen allclose all
Plate incorporation – average number of revertants per plate (mean of 2 plates).
Experiment 1
Treatment µg/plate |
TA98 |
TA100 |
TA1535 |
TA1537 |
WP2 uvrA |
|||||
-S9 |
+S9 |
-S9 |
+S9 |
-S9 |
+S9 |
-S9 |
+S9 |
-S9 |
+S9 |
|
Solvent control |
15 |
13 |
147 |
164 |
16 |
13 |
4 |
8 |
21 |
18 |
1.5 |
17 |
13 |
160 |
147 |
18 |
12 |
6 |
6 |
18 |
18 |
5.0 |
16 |
14 |
164 |
175 |
19 |
9 |
1 |
8 |
22 |
24 |
15 |
16 |
17 |
140 |
120 |
15 |
11 |
8 |
4 |
19 |
14 |
50 |
13 |
14 |
177 |
156 |
17 |
13 |
6 |
5 |
19 |
21 |
150 |
15 |
18 |
155 |
156 |
22 |
12 |
7 |
6 |
24 |
24 |
500 |
12 |
15 |
172 |
171 |
15 |
12 |
8 |
9 |
24 |
18 |
1500 |
14 |
17 |
149 |
153 |
11 |
7 |
4 |
9 |
23 |
20 |
5000 |
14 |
16 |
179 |
175 |
15 |
9 |
7 |
5 |
21 |
21 |
Positive control |
144 |
454 |
540 |
553 |
369 |
121 |
923 |
131 |
166 |
242 |
Plate incorporation – average number of revertants per plate (mean of 3 plates).
Experiment 2
Treatment µg/plate |
TA98 |
TA100 |
TA1535 |
TA1537 |
WP2 uvrA |
|||||
-S9 |
+S9 |
-S9 |
+S9 |
-S9 |
+S9 |
-S9 |
+S9 |
-S9 |
+S9 |
|
Solvent control |
31 |
17 |
183 |
184 |
20 |
17 |
10 |
8 |
23 |
23 |
50 |
18 |
18 |
189 |
173 |
16 |
16 |
6 |
10 |
21 |
19 |
150 |
28 |
16 |
199 |
172 |
16 |
18 |
11 |
11 |
27 |
24 |
500 |
24 |
12 |
171 |
180 |
12 |
18 |
11 |
7 |
25 |
20 |
1500 |
26 |
17 |
189 |
193 |
18 |
16 |
6 |
10 |
22 |
25 |
5000 |
28 |
19 |
167 |
198 |
16 |
20 |
6 |
10 |
20 |
23 |
Positive control |
194 |
666 |
607 |
660 |
436 |
125 |
1154 |
185 |
127 |
278 |
Summary table of cytogenetic analysis of CHO cells in the absence and presence of metabolic activation
Treatment µg/ml |
S9 Activation |
Treatment time |
Mean mitotic index (1000 cells) |
Cells scored (total no. metaphases) |
Mean aberrations per cell |
Cells with aberrations |
|
Numerical (%) |
Structural (%) |
||||||
Solvent control |
- |
4 |
11.2 |
200 |
0.000 |
0.0 |
0.0 |
2.5 |
- |
4 |
9.9 |
200 |
0.005 |
0.0 |
0.5 |
5 |
- |
4 |
9.8 |
200 |
0.000 |
0.5 |
0.0 |
12.5 |
- |
4 |
9.3 |
200 |
0.000 |
0.0 |
0.0 |
Positive control |
- |
4 |
5.2 |
200 |
0.370 |
0.0 |
20.0 |
|
|
|
|
|
|
|
|
Solvent control |
+ |
4 |
10.9 |
200 |
0.005 |
0.5 |
0.5 |
10 |
+ |
4 |
10.5 |
200 |
0.000 |
0.5 |
0.0 |
20 |
+ |
4 |
10.4 |
200 |
0.000 |
0.0 |
0.0 |
75 |
+ |
4 |
10.4 |
200 |
0.000 |
0.5 |
0.0 |
Positive control |
+ |
4 |
3.3 |
200 |
0.350 |
1.5 |
18.0 |
|
|
|
|
|
|
|
|
Solvent control |
- |
20 |
10.9 |
200 |
0.000 |
0.0 |
0.0 |
5 |
- |
20 |
8.9 |
200 |
0.005 |
0.0 |
0.5 |
10 |
- |
20 |
8.9 |
200 |
0.005 |
0.5 |
0.5 |
15 |
- |
20 |
5.5 |
200 |
0.000 |
0.0 |
0.0 |
Positive control |
- |
20 |
7.0 |
200 |
0.300 |
1.0 |
18.0 |
|
|
|
|
|
|
|
|
Table 1 Summary of mouse lymphoma mutagenicity results
| Test substance concentration µl/ml | Activation | Relative growth % | Mutant frequency x 10E-06 |
| Solvent control | -MA | 100 | 23.7 |
| Negative control | -MA | 87.7 | 17.2 |
| Positive control | -MA | 20.3 | 515.5 |
| 0.0125 | -MA | 86.8 | 18.5 |
| 0.025 | -MA | 73.1 | 15.8 |
| 0.05 | -MA | 92.3 | 22.3 |
| 0.1 | -MA | 62.0 | 9.5 |
| 0.2 | -MA | 29.5 | 28.1 |
| Solvent control | +MA | 100 | 29.9 |
| Negative control | +MA | 94.9 | 23.1 |
| Positive control | +MA | 25.1 | 196.0 |
| 0.0125 | +MA | 90.4 | 42.1 |
| 0.025 | +MA | 68.4 | 26.3 |
| 0.05 | +MA | 72.5 | 40.3 |
| 0.1 | +MA | 90.4 | 21.1 |
| 0.2 | +MA | 0.1 | 50.7 |
Table 1 Preliminary toxicity test
Concentration (μg/ml)
|
% RSG (-S9) 4-Hour Exposure
|
% RSG (+S9) 4-Hour Exposure
|
% RSG (-S9) 24-Hour Exposure
|
0 |
100 |
100 |
100 |
12.14 |
74 |
96 |
72 |
24.27 |
90 |
96 |
26 |
48.55 |
83 |
84 |
0 |
97.09 |
100 |
68 |
0 |
194.19 |
95 |
82 |
1 |
388.38 |
94 |
102 |
1 |
776.75 |
108 |
98 |
1 |
1553.5 |
100 |
102 |
4 |
3107 |
97 |
82 |
39 |
%RSG= Relative Suspension Growth
Table 2 Summary of results from main experiment, 4 h exposure
Treatment (μg/ml)
|
4-Hours-S-9 |
Treatment (μg/ml)
|
4-Hours+S-9
|
||||
%RSG |
RTG |
MF |
%RSG |
RTG |
MF |
||
0 |
100 |
1.00 |
89.99 |
0 |
100 |
1.00 |
114.53 |
12.5 |
112 |
1.29 |
89.46 |
12.5 |
113 |
1.04 |
91.57 |
25 |
111 |
1.28 |
82.23 |
25 |
106 |
1.20 |
95.58 |
50 |
121 |
1.42 |
89.78 |
50 |
102 |
1.05 |
101.72 |
100 P |
110 |
1.28 |
79.77 |
100 |
105 |
1.09 |
93.79 |
150 P |
109 |
1.28 |
86.92 |
150 P |
104 |
1.10 |
88.74 |
200 P |
122 |
1.38 |
86.12 |
200 P |
106 |
1.17 |
98.22 |
Linear trend NS |
Linear trend NS |
||||||
Positive control |
94 |
0.81 |
710.52 |
2 |
65 |
0.29 |
935.61 |
P Precipitate observed at the end of the exposure period.
* Not plated for viability or 5-TFT resistance
%RSG = Relative Suspension Growth
RTG = Relative Total Growth
MF = 5-TFT resistant mutants/106 viable cells 2 days after treatment
Table 3 Summary of results from main experiment, 24 h exposure
Treatment (μg/ml)
|
24-Hours-S-9 |
||
%RSG |
RTG |
MF |
|
0 |
100 |
1.00 |
96.68 |
1.56 * |
109 |
|
|
3.13 |
102 |
0.95 |
108.38 |
6.25 |
101 |
1.29 |
76.85 |
12.5 |
104 |
1.21 |
113.47 |
18.75 |
89 |
1.02 |
93.93 |
25 |
59 |
0.69 |
89.82 |
37.5 |
16 |
0.14 |
141.03 |
50 * |
9 |
|
|
Linear trend NS |
|||
Positive control |
92 |
0.69 |
992.94 |
* Not plated for viability or 5-TFT resistance
%RSG = Relative Suspension Growth
RTG = Relative Total Growth
MF = 5-TFT resistant mutants/106 viable cells 2 days after treatment
Endpoint conclusion
- Endpoint conclusion:
- no adverse effect observed (negative)
Genetic toxicity in vivo
Description of key information
Mammalian Bone Marrow Chromosome Aberration Test in rat (ip study): read-across from structural analogue hexamethyldisiloxane: Negative (similar to OECD TG 475) (DCC (1991)).
Link to relevant study records
- Endpoint:
- in vivo mammalian somatic cell study: cytogenicity / bone marrow chromosome aberration
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- 1980-11-26 to 1981-09-28
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- guideline study
- Qualifier:
- equivalent or similar to guideline
- Guideline:
- OECD Guideline 475 (Mammalian Bone Marrow Chromosome Aberration Test)
- Deviations:
- yes
- Remarks:
- only male animals used. Number of cells counted for determination of mitotic index not indicated - probably ca. 100, should be 1000
- Principles of method if other than guideline:
- The test was performed according to the Rodent Bone Marrow Cytogenetic Assay as recommended by the Ad Hoc Committee on Chromosome Methodologies in Mutagen Testing (Toxicology and Applied Pharm 22: 269-275, 1972) with modifications per the EPA Gene-Tox Program Cytogenetics Committee (12/3 to 12/5, 1980, Washington D.C.).
- GLP compliance:
- not specified
- Type of assay:
- chromosome aberration assay
- Species:
- rat
- Strain:
- Sprague-Dawley
- Sex:
- male
- Details on test animals or test system and environmental conditions:
- TEST ANIMALS
- Age at study initiation: 14 - 16 weeks
- Weight at study initiation: 250 - 280 g for range finding. 290 - 430 g for cytogenetic study
- Housing: 6 per cage
- Diet (e.g. ad libitum): Charles River Agway
ENVIRONMENTAL CONDITIONS
- Temperature (°F): 68 ± 3°F
- Humidity (%): approx 50 - Route of administration:
- intraperitoneal
- Vehicle:
- - Vehicle(s)/solvent(s) used: paraffin oil
- Lot/batch no. (if required): A7M02
- Purity: Laboratory Grade - Duration of treatment / exposure:
- single treatment
- Frequency of treatment:
- Single IP injection
- Post exposure period:
- 6, 24 and 48 hours
- Dose / conc.:
- 255 mg/kg bw/day (nominal)
- Dose / conc.:
- 515 mg/kg bw/day (nominal)
- Dose / conc.:
- 1 030 mg/kg bw/day (nominal)
- No. of animals per sex per dose:
- 5 males/dose
- Control animals:
- yes, concurrent vehicle
- Positive control(s):
- - The positive control agent cyclophosphamide was included in the 24-hour group.
- Route of administration: IP Injection
- Doses / concentrations: 22 mg/kg bw - Tissues and cell types examined:
- Bone marrow from femur
- Details of tissue and slide preparation:
- CRITERIA FOR DOSE SELECTION: Based on two range finding studies conducted to determine the maximum dose the animals could tolerate.
Range finding studies: Range finding study 1: Animals Injected intraperitoneally with 1676, 504, 168 and 50 mg/kg and observed once a day for 7 days for signs of toxicity. Range finding study 2: 10 animals injected with 3911, 1825, 521, 183 and 52 mg/kg. In main study animals were sacrificed at 6, 24 and 48 hours
DETAILS OF SLIDE PREPARATION: Approximately 4 slides were prepared for each animal. The chromosomes were prepared by standard methods and Giemsa stained.
TREATMENT AND SAMPLING TIMES ( in addition to information in specific fields):
6h group: Stock solution of 321 mg/ml; volumes injected were 1.0, 0.5 and 0.25 ml, resulting in the following doses calculated from body weight: 1030 mg/kg +/- 3.2%; 515 mg/kg +/- 5.6%; 255 mg/kg +/- 1.2%
24 hour group: animals were injected with 1.0 or 0.5 ml of 321 mg/ml stock solution, or 1.0 ml of 91 mg/ml stock solution, resulting in the following doses calculated from body weight: 1030 mg/kg +/- 0.8%; 515 mg/kg +/- 5.6%; 255 mg/kg +/- 3.1%
48 hour group: animals were injected with 1.0 or 0.45 ml of 426 mg/ml stock solution, or 1 ml of 102 mg/ml stock solution. This resulted in the following doses calculated from body weight: 1030 mg/kg +/- 3.1%; 515 mg/kg +/- 9.3%; 255 mg/kg +/- 2.4%
METHOD OF ANALYSIS: metaphase cells analysed by projecting the negatives with a darkroom enlarger onto a white counter
OTHER: - Evaluation criteria:
- In general, a minimum of 100 metaphase cells from each animal were scored for incidence of chromosomal aberrations.
- Statistics:
- Statistical methods: Chi2 test for comparison of expected and observed distribution of the number of breaks; Wilcoxon test was used as a nonparametric test.
- Key result
- Sex:
- male
- Genotoxicity:
- negative
- Remarks:
- on mitotic index
- Toxicity:
- no effects
- Vehicle controls validity:
- valid
- Negative controls validity:
- not applicable
- Positive controls validity:
- valid
- Additional information on results:
- RESULTS OF RANGE-FINDING STUDY
- Dose range: Exp 1: 1676, 504, 168, 50 mg/kg. Exp 2: 3911, 1825, 521, 183, 52 mg/kg
- Clinical signs of toxicity in test animals: No deaths observed in initial study. In second study 3 of 10 animals dosed with 3911 mg/kg died, while all the other animals survived till terminal sacrifice.
- Harvest times: 7 days exp 1, 14 days exp 2.
- High dose with and without activation: 1676 exp 1, 3911 exp 2
RESULTS OF DEFINITIVE STUDY
See table 1 - Conclusions:
- Hexamethyldisiloxane has been tested for the induction of chromosome aberrations in rat bone marrow cells in a valid study. It did not induce chromosomal damage in the bone marrow cells of rats following i.p. injection. The test substance is considered to be non-clastogenic (negative for the induction of chromosome aberrations) in rat bone marrow cells under the conditions of the test.
Reference
Negative controls: frequencies of breaks were 0.54%, 2.49% and 1.47% at sacrifice at 6, 24 and 48 hours respectively.
Table 1:Results of chromosome analysis in rat bone marrow cells
|
Low dose (255 mg/kg bw) |
Mid dose (515 mg/kg bw) |
High dose (1030 mg/kg bw) |
|||||||
Sampling time (h) |
6 |
24 |
48 |
6 |
24 |
48 |
6 |
24 |
48 |
|
Number of cells evaluated |
500 approx |
500 approx |
500 approx |
500 approx |
500 approx |
500 approx |
500 approx |
500 approx |
500 approx |
|
|
|
|
|
|
|
|
|
|
||
Chromosome aberrations |
Gaps |
6 |
11 |
3 |
3 |
6 |
25 |
2 |
12 |
14 |
Breaks |
5 |
2 |
9 |
10 |
15 |
6 |
5 |
6 |
7 |
|
Other aberrations |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
|
Mitotic index (% range) |
2 – 5 |
2 - 5 |
1 - 4 |
2 - 4 |
2 - 5 |
4 - 7 |
1 - 6 |
3 - 5 |
2 - 5 |
|
Polyploidy |
N.R |
N.R |
N.R |
N.R |
N.R |
N.R |
N.R |
N.R |
N.R |
|
Endo reduplication |
N.R |
N.R |
N.R |
N.R |
N.R |
N.R |
N.R |
N.R |
N.R |
|
N.R = Not Reported
Endpoint conclusion
- Endpoint conclusion:
- no adverse effect observed (negative)
Additional information
Data are available for octamethyltrisiloxane (L3) from reliable in vitro studies for mutagenicity to bacteria and cytogenicity in mammalian cells. No further information is available for the registered substance; however, reliable data are available for the closely related substances hexamethyldisiloxane (L2, CAS 107-46-0) and decamethyltetrasiloxane (L4, CAS 141-62-8). Octamethyltrisiloxane and decamethyltetrasiloxane both hydrolyse slowly to trimethylsilanol (measured) and dimethylsilanediol; hexamethyldisiloxane hydrolyses slowly (measured) to trimethylsilanol. Neither siloxanes nor silanols/silanediols are likely to contribute to genetic toxicity, and both registered and analogue substances have short hydrocarbon side-chains. It is therefore considered appropriate to read-across the in vitro mammalian cytogenicity and in vivo chromosome aberration results from hexamethyldisiloxane and decamethyltetrasiloxane to the registered substance. Additional information is given in a supporting report (PFA (2012aa)) attached in Section 13 of the IUCLID 6 dossier.
L4 was selected as read-across substance because it has the same hydrolysis products as L3, and both substances hydrolyse slowly (see Section 4.1.1.1). L2 was chosen as read-across substance to add in vivo information; it hydrolyses slowly to produce one of the two hydrolysis products of L3 and L4. None of the substance has any functional groups that are associated with genetic toxicity. The genetic toxicity data available for other substances from the analogue group are summarised in the Table below. The results of all the studies available at present for this analogue group are in agreement.
CAS |
Name |
Bacterial Mutagenicity |
In Vitro Mammalian Cytogenicity |
In Vitro Mammalian Mutagenicity |
In Vivo Genotox |
107-46-0 |
Hexamethyldisiloxane |
Negative Shin-Etsu (1994) |
Negative Shin-Etsu (1995) |
Negative Litton Bionetics (1978a) |
Negative in chromosome aberration assay Dow Corning Corporation (1982)
|
107-51-7 |
Octamethyltrisiloxane |
Negative Wagner, V. O. (2008) |
Negative Madraymootoo, W. and Rao, M. (2008) |
No data |
No data |
141-62-8 |
Decamethyltetrasiloxane |
Negative Wagner, V. O., Hines, R. M,. (2005) |
No data |
Negative Flanders L (2010) |
No data |
141-63-9 |
Dodecamethylpentasiloxane |
No data |
Results inconclusive |
No data |
No data |
Octamethyltrisiloxane has been tested for mutagenicity to bacteria in a study which was conducted according to OECD 471, and in compliance with GLP (Wagner (2008)). No evidence of a test substance related increase in the number of revertants was observed with or without activation in the initial or the repeat experiments with Salmonella typhimurium strains TA 98, 100, 1535, 1537 and E.coli WP2 uvrA. Appropriate positive and solvent controls were tested and gave expected results. It is concluded that the test substance is negative for mutagenicity to bacteria under the conditions of the test.
Information on the potential of octamethyltrisiloxane for clastogenicity to mammalian cells is available from a reliable in vitro cytogenetic assay conducted according to OECD TG 473 and under GLP (Madraymootoo and Rao (2008)). The test substance did not induce statistically and biologically significant increases in the chromosomal aberration frequency in CHO cells. Appropriate solvent and positive controls were included and gave expected results. It is concluded that the test substance is negative for the induction of chromosome aberrations in vitro (is not clastogenic) under the conditions of the test.
No information is available for octamethyltrisiloxane from studies on mutagenicity to mammalian cells, but the related substance, hexamethyldisiloxane, has been tested for mutagenicity to L5178Y cells in a reliable study according to a protocol that is similar to OECD TG 476 (Litton Bionetics (1978)). The original study and the read-across are considered to be reliability 2. The test substance did not cause a biologically significant increase in the mutation frequency; solvent and positive controls gave expected results. It is concluded that the test substance is not mutagenic under the conditions of the test.
Further information on mutagenicity to mammalian cells is available from another structural analogue, decamethyltetrasiloxane, which has been tested according to OECD TG 476 and under GLP conditions for mutagenicity to mouse lymphoma L5178Y cells up to cytotoxic concentrations (Flanders, L. (2010)). The original study was considered reliability 1. No increase in mutant frequency was detected at any concentration after 4h exposure with and without metabolic activation and 24 h exposure without metabolic activation. Appropriate solvent and positive controls were included and gave expected results. It is concluded that the test substance is negative for the induction of mutations in L5178Y cells under the conditions of the test.
The structural analogue hexamethyldisiloxane has also been tested for the induction of chromosome aberrations in rat bone marrow cells in a valid in vivo study (DCC (1991)). No induction of chromosomal damage in the bone marrow cells of rats was observed
following i.p. injection of the test substance. The test substance is considered to be non-clastogenic (negative for the induction of chromosome aberrations) in rat bone marrow cells under the conditions of the test. The original study and the read-across are
considered to be reliability 1.
The results of all the studies are in agreement.
Justification for classification or non-classification
Based on the available in vitro and in vivo genotoxicity data, octamethyltrisiloxane is not classified for mutagenicity according to Regulation (EC) No 1272/2008.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.
Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
